The techniques of nucleic acid hybridization and DNA transfection are being used to determine the sites of integration of baboon viral DNA in human cells. Available evidence indicates that human chromosomes 6 is the preferred site for baboon endogenous virus DNA integration. The viral DNA integrated at the "specific site" will be enriched and cloned by recombinant DNA techniques. These cloned viral DNAs will be used to probe for viral sequences in normal and neoplastic human and other primate tissues.